Speaker: Robert Yee MD --- Merrill Grayson Professor and Chair of Ophthalmology, IU School of Medicine Emeritus, Scientech member (Email: ryee@iu.edu) (Sponsored By: Robert Yee MD)(ID: 1915)
The human eye and brain's visual system do not function like a camera, as is commonly believed. In the retina, viewed images stimulate light-sensitive cells (rods and cones) and help brain cells in the first parts of visual system to break down the seen image into light/dark contrasts at different spatial frequencies, and detect edges and orientation of lines. Beyond these basic visual brain regions, other higher-order areas respond to motion, color, faces, objects and text/numbers. Injury to these latter areas, from strokes, infections or dementia, produce selective deficits (visual agnosias) for identifying and detecting particular image features - such as not being able to perceive or recognize faces (prosopagnosia). The many different types of visual agnosias demonstrate the intricate and complex arrangement of brain functions in the so-called "association areas" of the visual system.
Program: Live and Zoom: There’s More to Vision than Meets the Eye: Visual Agnosia
Speaker: Robert Yee, MD, Merrill Grayson Professor Emeritus of Ophthalmology; former Chair, Department of Ophthalmology, IUSM; Scientech Club member
Introduced By: Andy Ratermann
Attendance: NESC: 108, Zoom: 29
Guest(s): Christine Baldwin, Robert Baldwin, Lynn Chreist, Bob Chreist, Jessica Ellis, Linda Yee
Scribe: Terry Ihnat
Editor: Carl Warner
View a Zoom recording of this talk at:
Today's Program 111124
Visual Agnosia refers to a condition in which the normal pathways from the visual cortex to other areas of the brain are interrupted. It can be caused by trauma, stroke, infection, some forms of dementia, and is permanent.
Pathways from the visualized object start at the retina with its rods and cones, bipolar cells, and ganglion cells. All these specialized neurons are feeding signals to the optic nerve, optic tract, leading to the lateral geniculate nucleus and then to the striate cortex in the occipital lobe. From there, impulses are sent to other parts of the brain to process the visual input.
Visual agnosia may affect orientation in the space of what we see, recognition of objects such as faces, integration of parts, and depth perception. Prosopagnosia (facial blindness) can result from trauma, and the ability to recognize faces, including one’s own, is affected.
Robert Yee
